Add example showing all the eeg helmets

doc/whats_new.rst

@@ -19,7 +19,9 @@ Current
 Changelog
 ~~~~~~~~~
 
-- Add new tutorial on :ref:`sphx_glr_auto_tutorials_plot_eeg_no_mri.py` by `Alex Gramfort`_, and `Joan Massich`_
+- Add example on how to load standard montage :ref:`plot_montage` by `Joan Massich`_
+
+- Add new tutorial on :ref:`plot_eeg_no_mri` by `Alex Gramfort`_, and `Joan Massich`_
 
 - Add convenience ``fsaverage`` subject dataset fetcher / updater :func:`mne.datasets.fetch_fsaverage` by `Eric Larson`_
 

examples/visualization/plot_montage.py

@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+"""
+.. _plot_montage:
+
+Plotting sensor layouts of EEG Systems
+======================================
+
+This example illustrates how to load all the EEG system montages
+shipped in MNE-python, and display it on fsaverage template.
+"""  # noqa: D205, D400
+# Authors: Alexandre Gramfort <[email protected]>
+#          Joan Massich <[email protected]>
+#
+# License: BSD Style.
+
+from mayavi import mlab
+import os.path as op
+
+import mne
+from mne.channels.montage import get_builtin_montages
+from mne.datasets import fetch_fsaverage
+from mne.viz import plot_alignment
+
+subjects_dir = op.dirname(fetch_fsaverage())
+
+###############################################################################
+# check all montages
+#
+
+for current_montage in get_builtin_montages():
+
+    montage = mne.channels.read_montage(current_montage,
+                                        unit='auto',
+                                        transform=False)
+
+    info = mne.create_info(ch_names=montage.ch_names,
+                           sfreq=1,
+                           ch_types='eeg',
+                           montage=montage)
+
+    fig = plot_alignment(info, trans=None,
+                         subject='fsaverage',
+                         subjects_dir=subjects_dir,
+                         eeg=['projected'],
+                         )
+    mlab.view(135, 80)
+    mlab.title(montage.kind, figure=fig)

mne/channels/montage.py

@@ -26,7 +26,7 @@
 from ..io.open import fiff_open
 from ..io.constants import FIFF
 from ..utils import (_check_fname, warn, copy_function_doc_to_method_doc,
-                     _clean_names)
+                     _clean_names, _check_option)
 
 from .layout import _pol_to_cart, _cart_to_sph
 
@@ -132,9 +132,9 @@ def read_montage(kind, ch_names=None, path=None, unit='m', transform=False):
     path : str | None
         The path of the folder containing the montage file. Defaults to the
         mne/channels/data/montages folder in your mne-python installation.
-    unit : 'm' | 'cm' | 'mm'
-        Unit of the input file. If not 'm' (default), coordinates will be
-        rescaled to 'm'.
+    unit : 'm' | 'cm' | 'mm' | 'auto'
+        Unit of the input file. When 'auto' the montage is normalized to
+        a sphere of radius equal to the average brain size. Defaults to 'auto'.
     transform : bool
         If True, points will be transformed to Neuromag space. The fidicuals,
         'nasion', 'lpa', 'rpa' must be specified in the montage file. Useful
@@ -209,6 +209,8 @@ def read_montage(kind, ch_names=None, path=None, unit='m', transform=False):
 
     .. versionadded:: 0.9.0
     """
+    _check_option('unit', unit, ['mm', 'cm', 'm', 'auto'])
+
     if path is None:
         path = op.join(op.dirname(__file__), 'data', 'montages')
     if not op.isabs(kind):
@@ -332,12 +334,16 @@ def read_montage(kind, ch_names=None, path=None, unit='m', transform=False):
                          kind)
     selection = np.arange(len(pos))
 
-    if unit == 'mm':
+    if unit == 'auto':  # rescale to 0.085
+        pos -= np.mean(pos, axis=0)
+        pos = 0.085 * (pos / np.linalg.norm(pos, axis=1).mean())
+    elif unit == 'mm':
         pos /= 1e3
     elif unit == 'cm':
         pos /= 1e2
-    elif unit != 'm':
-        raise ValueError("'unit' should be either 'm', 'cm', or 'mm'.")
+    elif unit == 'm':  # montage is supposed to be in m
+        pass
+
     names_lower = [name.lower() for name in list(ch_names_)]
     fids = {key: pos[names_lower.index(fid_names[ii])]
             if fid_names[ii] in names_lower else None

tutorials/plot_eeg_no_mri.py

@@ -1,5 +1,7 @@
 # -*- coding: utf-8 -*-
 """
+.. _plot_eeg_no_mri:
+
 EEG forward operator with a template MRI
 ========================================
 
@@ -10,6 +12,8 @@
                subject will be less accurate. Do not over interpret
                activity locations which can be off by multiple centimeters.
 
+.. note:: :ref:`plot_montage` show all the standard montages in MNE-Python.
+
 .. contents:: This tutorial covers:
    :local:
    :depth: 2